Abstract : Food animals are a potential source of CTX-M resistance genes for human pathogens. We evaluated the transfer of the blaCTX-M-9 gene from animal strain of Salmonella enterica Virchow to Enterobacteriaceae of the human intestinal flora, using human flora-associated rats (HFA-rat) with and without cefixime treatment. In the absence of antibiotic, no transconjugant enterobacteria were found in the feces of HFA-rats. However, the transfer rate was high if Escherichia coli J5 recipient strains were co-inoculated orally with Salmonella. S. enterica Virchow persisted in the rat fecal flora, both during and after treatment with therapeutic doses of cefixime. The drug did not increase the transfer rate and E. coli J5-transconjugants were eliminated from the flora before the end of cefixime treatment. No cefixime was recovered in the rat feces. In the presence of recipient strains, the blaCTX-M-9 resistance gene was transferred from a strain of animal origin to the human intestinal flora, although transconjugant colonization was transient. Antibiotic use enhanced the persistence of donor strains, increasing the resistance gene pool and the risk of its spread.